In the semiconductor industry, one of the most widely used types of circuitry are the CMOS, or complementary, circuits. Complementary circuits generally include an n-conduction transistor and a p-conduction transistor in series. This connection results in very low static power consumption and, as a result, the circuits use very low power and are very efficient.
The major problem with these circuits is the number of process steps required during fabrication. Each of the two types of transistors requires different materials in the construction. For example, the process must start with some type of semiconductor substrate, generally n-conduction. The p-conduction transistor is formed in the n-conduction semiconductor substrate in a normal fashion. A n-conduction transistor is formed by first providing a large p-conduction tub in the semiconductor substrate and then fabricating the n-conduction transistor in the p-conduction tub. This process requires many extra steps and is, therefore, relatively expensive and labor intensive. Also, additional substrate area is required for deep implants and the like to protect the structure from random and inadvertent p-n-p-n diodes which are formed between the two types of transistors.
Also, in many instances it would be desirable to fabricate semiconductor circuits on materials, or supporting substrates, different than semiconductor substrates. In a typical example, there is presently a great deal of interest in providing financial cards, such as credit and debit cards, with semiconductor circuits which can perform various functions dealing with the use of the card. However, financial cards are generally formed of flexible plastic with a relatively low melting point and the fabrication of semiconductor circuits on semiconductor substrates, or other substrates, requires relatively high temperatures. Thus, at present the semiconductor substrates must be fabricated on semiconductor substrates and then mounted on the financial cards. This is unsatisfactory because of the difference in temperature coefficients and the potential flexing of the cards, both of which are highly detrimental to the safe and continued operation of the semiconductor circuit.
Accordingly, it would be highly advantageous if complementary semiconductor circuits could be formed with fewer steps and at lower temperatures.
It is a purpose of the present invention to provide a new and improved method of fabricating inorganic and organic transistors on a common substrate.
It is a further purpose of the present invention to provide a new and improved method of fabricating complementary transistors at relatively low temperatures and with a substantial reduction in the number of processing steps.
It is another purpose of the present invention to provide new and improved complementary transistors which can be fabricated on supporting substrates such as plastic and the like.